Practically every key on the SwiftKey X keyboard can be long-pressed to enter numbers and common symbols. Unfortunately, there’s no way to custom-map buttons so that the symbols you select will be entered after a long key press.
Like SwiftKey X, most of the Thumb keys double as symbol buttons through a long press, but users can change this secondary function to suit their needs. For example, we made the Z key also enter a comma instead of the standard “/.” The Text Shortcut feature lets you create and enter canned text for often-used message topics. Custom keys can also be added and bound to a software button bar above the keyboard.
Winner: Thumb Keyboard.
The amount of control for adjusting keys offered by Thumb unquestionably trumps SwiftKey X.